Engine starter drive



- Oct 15, i935# w. L MCGRATH 2,017,5@6

@News STARTER DRIVE Filed Juni; 13,A 19:54

INVENTOR ATTORNE Patented Oct. 15, 1935 UNITED STATES 2,017,566 l ENGINESTARTER DRIVE William L. McGrath, Elmira, N. Y., assignor to EclipseMachine Company, Elmira Heights, N. Y., a corporation of New YorkApplication June 13, 1934, Serial No. 730,517

24 Claims.

This invention relates to an engine starter drive and `more particularlyto that type of starting gearing which automatically connects a startingmotor to an engine to be started, and disconnects the same when .theengine becomes selfoperative. 'Ihis application is a continuation inpart of vtheprior application of William L. Mc- Grath, Serial Number689,279, led September 13, 1933.

It is an object of the present invention to provide a novel starterdrive which is reliable and eiii'cient in operation and particularlyadapted to insure' smooth and continuous cranking under adverseconditions.

It is a further object to provide a construction in which the torque istransmitted in part through a yieldingdriving connection and in partthrough supplemental frictional clutching connections that areautomatically closed before cranking 20 torque is applied to theyielding driving connection.

It is a further object to provide a construction in'which the torque istransmitted in part through one or more frictional clutches that areautomatically closed before the cranking torque is applied to the drivespring, thus largely increasy,

ing the life of the spring and of the drive.

It is another object of the invention to provide such a device which isdesigned to resist pump- 30 ing of the driving pinion during cranking,toward and away from its fully engaged position as the engine passesover its compression points.

It is a further object to provide such a device embodying a torsionspring with radially flattened convolutions, and provisions for causingthe convolutions of the springY to be supported laterally while it istorqued.

Further objects and advantages will -be apparent from the followingdescription taken in connection with the accompanying drawing in which:

Fig. l is a side elevation partly in section of one embodiment of theinvention showing the parts in normal or idle position;

Fig. 2 is a similar view of a second embodiment of the inventionshowing-the parts in driving position;

Fig. 3 is a view similar to Fig. 2 showing the parts in the positionassumed in case a tooth of 1 ,I the pinion abuts a tooth of the enginegear; and

Fig. 4 is a similar view with the mounting.

sleeve elimina-ted and the screw shaft, driving head and stop for thecontrol member mounted directly on the armature shaft.

g Referring rst to Fig. l of the drawing, there (Cl. 'I4-7) is shown apower shaft I which is preferably the extended armature shaft of astarting motor, not shown. An engine driving member in the form of apinion 2 is slidably journalled on the shaft I and is arranged to bemoved longitudinally into 5 and out of engagement with a toothed membersuch as a flywheel gear 3 of the engine to be started, and to be rotatedfrom the power shaft in order to crank the engine.

Means for moving the pinion 2 into and out l0 of mesh with the enginegear and for rotating the same is provided comprising a hollow screwshaft 4 and a transmission member in the form of a nut 5 threadedthereon and rigidly connected -to the pinion 2 by means of a barrel 6which is 15 suitably fixed at its ends to the nut and pinion. Screwshaft 4 is freely journalled on a mounting and actuating member in theform of a hollow sleeve I5 on the power shaft. Shaft 4 is yieldablydriven from the power shaft I by means of a torsion spring 1 havingradially flattened convolul tions and suitably anchored to the screwshaft at one end as by means of a. stud 8, and to the power shaft I atits other end as by means of a bolt 9 traversing a driving head IIformed on or 25 fixed to the sleeve I5 and keyed -to the'power shaft I.Itl will be understood that the radial flattening of the convolutions ofthe spring renders the spring comparatively limber with respect to axialcompression, with increased torque capacity, as is well known in thisart. Space .I2 is provided between the endof the screw shaft 4 when innormal position and the abutment 'formed by the adjacent end of thedriving head l II in Aorrler to permit longitudinal movement of thescrew ,shaft toward the driving head against thecompression of thespring 1.

An abutment is provided in the form of a stop ring I3 for limiting thelongitudinal motion of the nut 5 in a direction to mesh the pinion 2 and40 for dening the normal position of the screwl shaft 4Y on sleeve I5.'I'he stop ring I3 is provided with an extended ange I4 telescoped over'the end of the screw shaft 4 in position to be engaged by the nut 5when in driving position, 45 vand is longitudinally fixed with respectto the power shaft I, by means of an abutment I6 on the sleeve I5 asshown in Fig. 1, or by means of a threaded connection with said sleeveas shown in Figs. 2 and 3. l

In order to prevent rebounding of the pinion and nut when they arethrown back to idle position after the engine starts, the screw shaft 4is provided with a smooth portion I1 adjacent the idle position of thenut which permits the nut to 55 run off the threads and rotate freely.Means for insuring reengagement of the nut with the threads of the screwshaft are provided in the form of a compression spring I8 locatedbetween the stop ring I3 and the pinion end of the barrel 6, whichspring is'under slight compression when the nut runs off the threads ofthe screw shaft.

Means for normally maintaining the nut in idle position is provided inthe form of a light compression spring I9 located between the nut andthe stop ring I3.

In the operation of this embodiment of the invention, rotation of thepower shaft I is transmitted through the torsion spring 1 to the screwshaft 4. The pinion and barrel assembly by reason of its inertia torotation, is moved longitudinally by the nut 5 until the pinion 2 isfully meshed with the engine gear 3 at which time the nut 5 engages thestop ring I3. The screw shaft 4 thereupon moves backward, compressingthe spring 'I until the space I2 is taken up, after which the pinion,nut and screw shaft are driven' from the power shaft I through thesupplementary frictional clutching connections established between theabutments on the sleeve I5 and the screw shaft 4 and nut 5 and throughthe spring 1, as indicated in Fig. l2. A ring 2| of ber or otherSuitable material is preferably provided between the abutting surfacesof the screw shaft and driving head which aids in .con-

trolling the supplemental frictional transmission and also preventsseizing of said surfaces.

When tre engine becomes self-operative, the acceleratiotl of the pinion2 by the engine gear causes the nut 5 to overrun the screw shaft,whereby the screw shaft is permitted to return to its normal positionunder the expansive action of the spring 1 and thereafter the nut 5 isthrown back to its idle position where it is permitted to overrun asabove described until its rotational momentum. has become dissipated.The spring I8 then serves to place the nut in initial engagement withthe screw threads in position for reaotuation as above set forth.

It will be noted that since the screw shaft 4 has been displacedlongitudinally and bears against the driving head I l during thecranking operation, any pumping action of the pinion as the enginepasses over its compression points is resisted by the friction betweenthe abutting surfaces of the nut, stop ring I3, and screw shaft.Moreover, `in case the tendency of the pinion to pump is not entirelyovercome by such friction, the screw shaft 4 may shuttle back and forthalong its longitudinal path of travel while the pinion 2 is still heldin its fully meshed position by the expansive force of spring 1, suchlongitudinal movement of the screw shaft being effectively damped by thefriction between the threads of the screw shaft and the nut 5.

It is `further to b e noted that the compression of spring 'I prior tothe application of the cranking load causes the convolutions of thespring to be brought into supporting relation with each other, so thatthe tendency of the flattened convolutions to tip over when the springis torqued, is overcome. Moreover, the friction produced between theconvolutions of the spring when it is compresed and torqued assists indamping the torsional vibrations of the spring. It will be understoodthat whetheror not the spring 'I is compressed solid as indicated inFig. 2 when the screw shaft is forced against the driving abutment II bythe screw jack action of the nut 5, the frictional engagement betweenthe convolutions of the spring will be produced when the spring istorqued. These features have been found to increase the durability andefliciency of the spring.

-In the embodiment of the invention illustrated in Figs. 2 and 3, thesleeve I5' is formed integral with the driving head II, and the stopmember Iiiv is formed as a nut threaded on the end of the sleeve I5' andrigidly fixed thereon in any suitable way as indicated at 22. A ring I0of bronze or other suitable material and corresponding to the ringl 2|is preferably interposed as indicated between the nut 5 and stop memberI3'. The remaining parts are the same as illustrated in Fig. 1 and aresimilarly numbered, and the operation of the drive is the same as aboveset forth.

In case in the operation of the drive a tooth of the pinion cornes intoengagement with a tooth of the flywheel gear as illustrated in Fig. 3,the obstruction of the motion of the pinion 2 causes the screw shaft 4to move back, compressing the spring 1 and thereby causing the nut 5 tobind4 on the screw shaft and transmit torque to the pinion. The pinionis thus indexed and is thereupon snapped into mesh by the expansion ofthe spring 'I. Cranking then takes place as usual.

The construction shown in Fig. 4 functions in a similar manner. Theconstructional ldifferences are that the sleeve I5 is entirely omittedand the screw shaft 4, the drive head I I' and the stop or abutment I3are directly mounted on the armature shaft, the stop or abutment I3being fixed thereto by a suitable rigid connection. While thisembodiment lacks the unitary characteristic that the sleeve I5 impartsto the device, the functioning thereof, after once installed, issimilar.

It is particularly pointed out that by the present invention, withoutsacrificing the many advantages of a yielding driving connection in'theform of a torsion spring between the armature shaft and the hollow screwshaft through which heretofore all of the electrical torque and thekinetic energy of rotation of the armature and associated parts passed,a supplemental frictional transmission is automatically establishedbetween the armature shaft and the hollow screw shaft and between thearmature shaft and the pinion assemblage. This results from the novelmode of operation of the hollow screw shaft in this combination in thatit is automatically moved longitudinally in one direction in the normaloperation of the drive to subserve the functions of establishing thesupplemental frictional transmissions, as well as to compress the coilsof the drive spring into supporting relationship. This mode offunctionng has not only improved the operation of the drive in therespects noted but has increased the life of the drive spring and thedrive itself to a marked extent. shaft to move longitudinally in theopposite direction when the engine goes over compression and tends todemesh the pinion from the flywheel gear, insures that the pinionremains in fully meshed position.

The inventive idea is susceptible of various embodiments of which theforegoing are examples. The invention is not, however, limited thereto,the bounds thereof being set in the appended claims. It is expresslyunderstood with respect to said claims that, except in those in whichthe hollow shaft I5 is expressly stated as an element, the matter of thedirect or indirect mounting of the hollow screw shaft 4. the abutmentI3, I3. I3"

Further, the ability of the hollow screw and the drive head Il on thearmature shaft I is immaterial; and that the language of such claims ismeant to cover both constructions.

It is further pointedout that while the inventive idea subscrves itsmaximum benets and advantages when embodied in a drive employing atorsion spring between the drive head and the screw shaft for reasonsheretofore stated, so far as the new result of the automaticestablishment of supplementary clutching connections to transmit part ofthe torque by the longitudinal movement of the screw shaft in the normaloperation of the drive, this may be effected by a yieldable drivingconnection between the drive head and the screw shaft other than atorsion drive spring; and certain of the claims herein presented are notlimited to such a torsion or other spring but are directed broadly tothe automatic establishment of the supplementary clutching connectionsby the longitudinal movement of the screw shaft in combination with ayielding driving connection in the direct line of torque transmission.

What is claimed is:

1. In an engine starter, a unitary drive including a mounting andactuating member, a screw shaft loosely mounted thereon, a torsionspring connecting said mounting member and shaft, a nut threaded on thescrew shaft, an engine driving member connected for rotation andlongitudinal movement with the nut, and means on the mounting memberarranged to be engaged by said nut for hunting longitudinal movement ofthe nut in the direction to engage the engine driving member and fortransmitting driving torque from the mounting member to the nut.

2. In an engine starter, a unitary drive including a mounting andactuating member, a screw shaft loosely mounted thereon, a torsionspring connecting said mounting member and shaft, a. nut threaded on thescrew shaft, an engine driving member connected for rotation andlongitudinal movement with the nut, means on the mounting memberarranged to be engaged by said nut for limiting longitudinal movement ofthe nut in a direction to engage the engine driving member, and means onthe mounting member for limiting longitudinal movement ofthe screw shaftin the direction to compress the spring and for transmitting drivingtorque from the mounting member to the screw shaft in the normaloperation of the drive.

3. In an engine starter drive, a power shaft, a screw shaft looselymounted thereon, a torsion spring having normally spaced convolutionsanchored at one end to the power shaft and the other to the screw shaft,a nut threaded on the screw shaft, an engine driving member looselymounted on the power shaft, and connected for rotation and longitudinalmovement with the nut, an abutment on the power shaft limitinglongitudinal movement of the nut in the direction to mesh the pinion, anabutment on the power shaft for limiting longitudinal movement of thescrew shaft in the direction to compress the spring and for establishingtorque transmittingclutching relationship between the screw shaft andits abutment in the normal operation of the drive.

4. In an engine starter, a unitary drive including a mounting andactuating member, a screw shaft loosely mounted thereon, a torsionspring having normally spaced convolutions anchored at one end to themounting member and at the other to the screw shaft, a nut threaded onthe screw shaft, an engine driving member connected for rotation andlongitudinal movement with the nut.

an abutment on the mounting member arranged to be engaged by said nutfor limiting longitudinal movement of the nut in the direction to engagethe engine driving member, an abutment on the mounting member forhunting longitudinal movement of the screw shaft in the direction tocompress the spring and for establishing torque transmitting clutchingrelationship between the screw shaft and its abutment.

5. In an engine starter drive, a power shaft, an engine drivingmember'ioosely mounted thereon for movement into and out of engagementwith a member of the engine to be started, means including a coiledspring having normally spaced attened convolutions for actuating theengine,

screw shaft loosely mounted on the sleeve and yieldably connected forrotation and longitudinal movement therewith, a nut threaded on thescrew shaft and connected to actuate the engine driving member and astop on said sleeve independent of said screw shaft adapted to beengaged by said nut when in driving position.

.'7. In an engine starter drive, a power shaft, an engine driving memberloosely mounted thereon for longitudinal movement into and out ofengagement with a member of an engine to be started, a hollow sleevefixed to the power shaft, a hollow screw screw shaft loosely mounted onthe sleeve and yieldably connected for rotation and longitudinalmovement therewith, a nut threaded on the screw shaft and connected toactuate the engine driving member, a stop on said sleeve adapted to beengaged by'said nut when in driv- 4 ing position, and a stop on saidsleeve adapted to limit longitudinal motion of the screw shaft due tothe driving reaction of the nut.

8. In an engine starter drive, a power shaft, an engine driving memberloosely mounted thereon for longitudinal movement into and out o fengagement with a member of the engine to be started, a. hollow sleevefixed to the power shaft, a hollow screw shaft loosely mounted on thesleeve, a coiled spring having spaced convolutions anchored at its endsto said sleeve and screw shaft respectively, a nut threaded on the screwshaft and connected to actuate the engine driving member, a stop on saidsleeve adapted to be engaged by said nut when in driving position, and astop on said sleeve adapted to limit compression of said spring.

9. In an engine starter drive, a power shaft, an engine driving memberloosely mounted thereon for longitudinal movement into and out ofengagement with a member of the engine to `be started, a hollow screwshaft loosely mounted on the power shaft and yieldably connected theretofor rotation therewith and longitudinal movement with respect thereto, anut threaded on the screw shaft and connected to actuate the pinion, astop xed rigidly to the p ower shaft independent of said screw shaft tobe engaged by the nut when in driving position. a yielding connectionbetween the nut anld stop urging the nut toward idle position, saidscrew shaft having a smooth portion which permits the nut. to run of!the threads in its idle position, and yielding means between the stopand the engine driving member for insuring reengagement of the nut withthe threads.

.10. In an engine starter drive, a power shaft, a screw shaft looselymounted thereon, a driving head and an engine driving member alsomounted thereon, a yielding driving connection between said drive headand screw shaft, a control member threaded on said screw shaft andconnected to said driving member to rotate and move the samelongitudinally, and abutment means mounted on the 'power shaft limitingthe movement of said control member and cooperating therewith to causerelative rotation of the screw shaft and control member to move saidscrew shaft longitudinally and establish a torque transmitting clutchingrelationship between the screw shaft and the drive head in the normaloperation of the drive.

1l. In an engine starter drive, a power shaft, a screw shaft looselymounted thereon, a driving head and an engine driving member alsomounted thereon, a yielding driving connection between said drive headand screw shaft, a control member threaded on said screw shaft andconnected to said driving member to` rotate and move the samelongitudinally, and means including abutment means mounted on the powershaft limiting the movement of said control member and nected to saiddriving member to rotate andmove the same longitudinally, and meansincluding abutment means mounted on the power shaft limiting themovement of said control member and cooperating therewith to causerelative rotation of the screw shaft and control member to move saidscrew shaft longitudinally and establish a torquel transmittingclutching relationship between the screw shaft and the drive head andbetween said control means and abutment .means in the normal operationof the d rive.

13. In an engine starter drive, a power shaft, a screw shaft looselymounted thereon, a driving head and an engine driving member alsomounted thereon, a yielding driving connection between said drive headand screw shaft in the line of torque transmission, a control memberthreaded on said screw shaft and connected to said driving member torotate and move the same longitudinally, and abutment means mounted onthe power shaft limiting the movement of said cori'- trol member andcooperatingtherewith `to causev relative rotation of the screw shaft andcontrol member .to move said screw shaft longitudinally and establish atorque transmitting clutching relationship between the screw shaft andthe drive head in the normal operation of the drive.

14. In an engine starter drive, a power shaft, a screw shaft looselymounted thereon, a driving head and an engine driving member alsomounted thereon, a yielding driving connection between said drive headand 'screw shaft in the line of torque transmission, a control memberthreaded on said screw shaft and connected to said driving member torotate and move the same longitudinally; and means including abutmentmeans mounted on the power shaft limiting the movement of said controlmember and cooperating therewith to cause'relative rotation of the screwshaft and control member to move said screw shaft longitudinally andestablish a torque transmitting clutching relationship between the screwshaft and the drive head and between said conl trol means and abutmentmeans in the normal operation of the drive.

15. InI a engine starter drive, a power shaft, a screw shaft looselymounted thereon, yielding driving means connecting said shafts, anengine l5 driving member loosely mounted on said power shaft, a controlmember screw threaded on said screw shaft and connected to said drivingmember for rotation and longitudinal movement therewith, means on thepower shaft limiting longitudinal movement of said control member in onedirection and means on the power shaft limiting longitudinal movement ofthe screw shaft in the opposite direction and establishingtorquetransmitting clutching relationship between said Z5 control memberand its associated means and between the screw shaft and its associatedmeans in the normal operation of the drive.

16. In an engine starter drive, a power shaft, a screw shaft looselymounted thereon-for rotary and longitudinal movement with respectthereto, a yielding driving connection interposed between said shafts,engine driving means having threaded engagement with said screw shaftand capable of longitudinal movement and rotary movement relativethereto-to engage and crank the engine, stop means rigid with said powershaft for limiting the movement of said driving means in engine engagingdirection, and stop means rigid with said vpower shaft for limiting themovement of said screw shaft in the opposite direction, said stop meansand driving means and said stop means and screw shaft being adapted fortorque-transmitting engagement, and said threaded connection causingsaid driving means 4.'- and screw shaft to move in opposite directionsinto such engagement with their respective stop means prior to theapplication of cranking torque to said yielding driving connection.

17. In an engine starter drive, a power shaft, a screw shaft looselymounted thereon for rotary and longitudinal movement with respectthereto, a torsion drive spring connecting said shafts, engine drivingmeans having threaded engagement with said screw shaft and capable oflongitudinal movement and rotary movement relative thereto to engage andcrank the engine, stop means rigid with said power shaft for limitingthe movement of said driving means in engine engaging direction, andstop means rigid with said power shaft C0 for limiting the movement ofsaid screw shaft in the opposite direction, said stop means and drivingmeans and said stop means and screw shaft being adapted fortorque-transmitting engagement, and saidI threaded connection causingsaid driving means and 'screw shaft to move in opposite directions intosuch engagement with their respective stop means prior to theapplication of cranking torque to said drive spring.

18. In a st arter drive a power shaft, an engine driving member mountedfor movement into and out of engagement with a member of the engine tobestarted, a torque-transmitting connection between the power shaftfandthe engine driving member including a spring driving connection drivingmember mounted for movement into and out of engagement with a member ofthe engine to be started, a torque-transmitting connection between thepower shaft and the engine driving member including a yieldable drivingconnection and a friction clutch arranged in parallel, said clutch beingnormally disengaged, and means responsive to the total transmittedtorque for closing said clutch to supplement the transmission of torquethrough the yieldable driving connection.

20. In a starter drive a power shaft, an engine driving member, atorque-transmitting `connection between the power shaft and' enginedriving member including two yieldable driving connections in parallel,one being constantly effective to transmit torque, and the other beingnormally loose, and torque-responsive means Afor tightening the looseconnection to cause it to gradually assume the load.

21. In a starter drive a power shaft, an engine driving member, frictionclutch elements con, nected respectively to the power shaft anddrivingmember, load-responsive 'means for closing said clutch, and resilienttorque transmitting means located adjacent the friction clutch elementsfor controlling the engagement of said clutch elements.

22. In a starter drive a power shaft, an engine driving member, frictionclutch elements connected respectively to the power shaft and drivingmember, load responsive means for closing transmission of torque fromthe power shaft to the driving member located adjacent the frictionclutch elements for controlling the engageemnt of `said clutch elements.

23. In a starter drive a power shaft, an engine driving member mountedfor movement into and out of engagement with a member of the engine tobe started, clutch elements connected respectively to the power shaftand driving member, load-responsive means for closing said clutch andyieldable means normally maintaining said clutch elements disengaged andconnected between the power shaft and load responsive means to actuatesaid load-responsive'means to cause closure of the clutch.

24. A starter drive including a power member. an engine driving member,torque transmitting connections therebetween including normally A`looseclutch elements and a coiled spring, said clutch elements being arrangedto supplement the transmission of torque through said spring, and meansresponsive to the torque transmitted by said spring for closing saidclutch to relieve said spring from excessive loads.

WIILIAM L. MCGRATH.

`said clutch and resilient means in the line of 5

